I first came across Standard ML in Dan Grossman's Programming Language course on Coursera[1]. After previously trying Haskell and Scala, this is where the benefits of functional programming and static typing really clicked for me. Really wish the language had caught on outside of academia so I had an excuse to use it more. In addition to the implementations mentioned in the blog post, The University of Chicago created Manticore[2] and Tohoku University in Japan created SML#[3]
Thanks for sharing Manticore! I didn't mention SML# because most of the documentation is in Japanese and it's hard to find recent info. There is an unofficial fork on Github but it explicitly states that it is unofficial so... not something I'd recommend to a general audience.
Edit: nevermind! I checked out their docs again and it seems to be decently translated. I'm still not sure where their code is actually hosted, just that you can download releases. So added it to the list of major implementations!
[1] https://www.coursera.org/learn/programming-languages
[2] http://manticore.cs.uchicago.edu/
[3] https://www.pllab.riec.tohoku.ac.jp/smlsharp/